Stencil sheet



Se t. 20, 1927 9 9 9 j w. H. KURTH STENCIL SHEET Filed Dec. 6, 1926 INVEN TOR. 7n Jflau if A TTORNEYS.

Patented S ept I20, 192;. it

.UNITED STATES 1,643,019 PATENT OFFICE.

I WILLIAM KURTH, OF CHICAGO, ILLINOIS. ASSIGNOR TO THE HEYER DUPLIOATORgo. INC., OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

STENCIL SHEET.

This invention relates to an improved type of-stencil sheet and to aprocess for making the same, whereby a stencil sheet having certain newand desirable qualities is obtained. The object of this invention is toproduce a stencil sheet which requires no preliminary treatment to makeit take ex ceptionally clear impressions when struck by the blow of thetype of a typewriter, or

by a suitable scriber tool. Another object of this invention is toproduce a stencil sheet which will retain these desirable properties foran indefinite period, so that after long storage, the sheet is insubstantially the same condition as when originally made.

It has. been customary heretofore to prepare such stencil sheets bycoating a thin sheet'of fine paper, such as a high grade unsized tissuepaper, with a solution of some plastic material, such as cured gelatinand lycerin, or a plasticized cellulose ester. uch stencil sheets arenot entirely satisfactory, in that they either have to be moistenedbefore use, or where the cellulose ester is used, if a plasticiser isused, which is a solvent for the cellulose ester, the film has atendency to be sticky or tacky, while on the other hand, where certainnatural fats or oils are. used, which are not solvents for thenitrocellulose, such oils will become rancid on standing over aconsiderable length of time.

According to my invention, these difficulties are avoided by producingafilm consisting of two' phases, one of'which is a solid and one aliquid, somewhat in the nature of a colloid. The solid phase, which iscontinuous, has dispersed therein small liquid particles, so thatinstead of a tough continuous film on the paper, I have a spongy film 4which is cut by the blow from the type in the typewriter or a suitablescriber tool with extreme ease. Furthermore, the edges of such a mark asis produced, as described above, areextremely sharp in outline andpermanent in form. v

, To better disclose the invention, reference is madeto the accompanyingdrawing illustrating a section of my stencil sheet on a very muchenlarged scale; wherein A illustrates the continuous solid phase; B thedispersed liquid phase, and C the thin sheet of tissue paper.

' While many materials are suitable for the liquid or dispersed. phase.of my improved stencil sheet, I prefer to use such materials formula:

Application filed December 6, 1926. serial No. 152,806.

turning rancid by the addition of small amounts of sassafrassy oil ofcamphor. The oil, which is in small particles, each surrounded by a wallcomprising the solid continuous phase, is preserved indefinitely, sothat the finished stencil sheet may be stored over very long periods oftime without deteriorating. In the absence of a preservative, the oiltends to increase in acidity in becoming rancid, and the increasedacidity in turn causes the oil to attack the surrounding walls of thesolid phase and break down the honeycomb structure of the solid phase,which permits the globules of oil to coalesce, and thus in time torender the stencil sheet gummy or sticky, and unfit for use. Theaddition of the preservative agent prevents this acidifying ofthe oilglobules, and hence preserves the solid phase against disintegration, sothat the stencil sheet will retain its pliability and its otherqualities unimpaired for a long period of time. c

- While many materials are suitable for the solid continuous phase, Iprefer, on account of their uniformity and ease of handling, to use suchmaterials as may be dissolved in ordinary solvents which are likewisecompatible with solvents for the oil of the dispersed phase. I havefound that most of the cellulose esters are particularly adapted forthis purpose, since, when dissolved, and the solvent evaporated, theyform permanent and sufliciently tough films to permanently hold the oil.Furthermore, they are impervious to the oil, are flexible, and holdtheir form over very long periods of time.

' In order to make my invention clear, I

will now describe one preferred process which I have found satisfactoryfor producing my improved stencil sheet:

I take 20 parts, by weight, of a lacquer compounded according to thefollowing tion of thymolan 0.33 parts, by weight, of

sassafrassy oil of camphor. This mixture is then coated on a sheet offine unsized tissue paper in anysuitable manner, as by means of dipping,brushing or the like.

A sheet, prepared as described above, dries in a few minutes, to a pointwhere the oil begins to separate out into very small particles which aredispersed throughout the coating, since the oil used is not a solventfor the nitro-cellulose. The sheet, after thoroughly drying, is in acondition suitable for use as a. stencil sheet, and retains its pliable,soft form over long periods of time, and the oil does not become rancid.

I claim:

1. A stencil sheet comprising a fine, un-

sized tissue paper coated with a material comprising a solid, continuousphase impervious to oil, a liquid oily phase dispersed therein, and apreservative to prevent the oil from becoming rancid, and breaking downof the solid phase.

2. A stencil sheet comprising a fine, unsized tissue paper coated with amaterial comprising a solid, continuous phase impervious to oil, aliquid oily phase dispersed therein in particles of substantially colloidal size, and a preservative to prevent the oil from becoming rancid,and breaking down of the solid phase.

3. A stencil sheet comprising a fine, un-

sized tissue paper coated with a thin layer of cellulose estercomprising a solid, conaeaaoie tinuous phase impervious to oil, a liquidoily phase dispersed therein, and a preservative to prevent the oil frombecoming rancid, and breaking down of the solid phase.

4.. A stencil sheet comprising a fine, unsized tissue paper coated witha thin layer of cellulose ester comprising a solid, continuous phaseimpervious to oil, a liquid oily phase dispersed therein in particles ofsubstantially colloidal size, and a preservative to prevent the oil frombecoming rancid, and breaking down of the solid phase.

5.- A stencil sheet com rising a fine, unsized tissue paper coate with amaterial comprising a solid, continuous phase impervious to oil, aliquid oily phase dispersed therein, and a small amount of oilot'camphor to prevent rancidity of the liquid oily phase, and breaking downof the solid phase.

6. A stencil sheet comprising a fine, unsized tissue paper coated with amaterial comprising a solid, continuous phase impervious to oil, aliquid oily phase dispersed therein in particles of substantiallycolloidal size, and a small amount of oil of camphor to preventrancidity of the liquid oily phase,

and breaking down of the solid phase.

7. A' stencil sheet comprising a fine,unsized tissue paper coated with athin layer of cellulose ester comprising a solid, continuous phaselIIlPGIVlOllStO oil, a liquid oily phase dispersed therein, and a smallamount of oil of camphor to prevent rancidity of the liquid oily phase,and breaking down of the solid phase.

8. A stencil sheet comprising a fine, unsized tissue paper coated with athin layer of cellulose ester comprising a solid. continuous phaseimpervious to oil, a liquid oily phase dispersed therein in particles ofsubstantially colloidal size, and a small amount of oil of camphor toprevent rancidity of the liquid oily phase, and breaking down of thesolid base.

' W'JPLLIAM H. KURTH.

